PowerScale OneFS 9.5.0.0 Web Administration Guide

Environment

Depending on the environment you select, the system will automatically select the General ACL Settings and Advanced ACL Settings options that are optimal for that environment. You also have the option to manually configure general and advanced settings.

Balanced

Enables PowerScale cluster permissions to operate in a mixed UNIX and Windows environment. This setting is recommended for most PowerScale cluster deployments.

UNIX only

Enables PowerScale cluster permissions to operate with UNIX semantics, as opposed to Windows semantics. Enabling this option prevents ACL creation on the system.

Windows only

Enables PowerScale cluster permissions to operate with Windows semantics, as opposed to UNIX semantics. Enabling this option causes the system to return an error on UNIX chmod requests.

Custom environment

Allows you to configure General ACL Settings and Advanced ACL Settings options.

General ACL Settings

ACL Creation Through SMB

Specifies whether to allow or deny creation of ACLs over SMB. Select one of the following options:

Do not allow ACLs to be created through SMB

Prevents ACL creation on the cluster.

Allow ACLs to be created through SMB

Allows ACL creation on the cluster.

NOTE:Inheritable ACLs on the system take precedence over this setting. If inheritable ACLs are set on a folder, any new files and folders that are created in that folder inherit the folder's ACL. Disabling this setting does not remove ACLs currently set on files. If you want to clear an existing ACL, run the chmod -b <mode> <file> command to remove the ACL and set the correct permissions.

Use the chmod Command On Files With Existing ACLs

Specifies how permissions are handled when a chmod operation is initiated on a file with an ACL, either locally or over NFS. This setting controls any elements that affect UNIX permissions, including File System Explorer. Enabling this policy setting does not change how chmod operations affect files that do not have ACLs. Select one of the following options:

Remove the existing ACL and set UNIX permissions instead

For chmod operations, removes any existing ACL and instead sets the chmod permissions. Select this option only if you do not need permissions to be set from Windows.

Remove the existing ACL and create an ACL equivalent to the UNIX permissions

Stores the UNIX permissions in a new Windows ACL. Select this option only if you want to remove Windows permissions but do not want files to have synthetic ACLs.

Remove the existing ACL and create an ACL equivalent to the UNIX permissions, for all users/groups referenced in old ACL

Stores the UNIX permissions in a new Windows ACL only for users and groups that are referenced by the old ACL. Select this option only if you want to remove Windows permissions but do not want files to have synthetic ACLs.

Merge the new permissions with the existing ACL

Merges permissions that are applied by chmod with existing ACLs. An ACE for each identity (owner, group, and everyone) is either modified or created, but all other ACEs are unmodified. Inheritable ACEs are also left unmodified to enable Windows users to continue to inherit appropriate permissions. However, UNIX users can set specific permissions for each of those three standard identities.

Deny permission to modify the ACL

Prevents users from making NFS and local chmod operations. Enable this setting if you do not want to allow permission sets over NFS.

Ignore operation if file has an existing ACL

Prevents an NFS client from changing the ACL. Select this option if you defined an inheritable ACL on a directory and want to use that ACL for permissions.

CAUTION:If you try to run the chmod command on the same permissions that are currently set on a file with an ACL, you may cause the operation to silently fail. The operation appears to be successful, but if you were to examine the permissions on the cluster, you would notice that the chmod command had no effect. As an alternative, you can run the chmod command away from the current permissions and then perform a second chmod command to revert to the original permissions. For example, if the file shows 755 UNIX permissions and you want to confirm this number, you could run chmod 700 file; chmod 755 file.

ACLs Created On Directories By the chmod Command

On Windows systems, the ACEs for directories can define detailed inheritance rules. On a UNIX system, the mode bits are not inherited. Making ACLs that are created on directories by the chmod command inheritable is more secure for tightly controlled environments but may deny access to some Windows users who would otherwise expect access. Select one of the following options:

• Make ACLs inheritable
• Do not make ACLs inheritable

Use the chown/chgrp On Files With Existing ACLs

Changes the user or group that has ownership of a file or folder. Select one of the following options:

Modify only the owner and/or group

Enables the chown or chgrp operation to perform as it does in UNIX. Enabling this setting modifies any ACEs in the ACL associated with the old and new owner or group.

Modify the owner and/or group and ACL permissions

Enables the NFS chown or chgrp operation to function as it does in Windows. When a file owner is changed over Windows, no permissions in the ACL are changed.

Ignore operation if file has an existing ACL

Prevents an NFS client from changing the owner or group.

NOTE:Over NFS, the chown or chgrp operation changes the permissions and user or group that has ownership. For example, a file that is owned by user Joe with rwx------ (700) permissions indicates rwx permissions for the owner, but no permissions for anyone else. If you run the chown command to change ownership of the file to user Bob, the owner permissions are still rwx but they now represent the permissions for Bob, rather than for Joe, who lost all of his permissions. This setting does not affect UNIX chown or chgrp operations that are performed on files with UNIX permissions, and it does not affect Windows chown or chgrp operations, which do not change any permissions.

Access checks (chmod, chown)

In UNIX environments, only the file owner or superuser has the right to run a chmod or chown operation on a file. In Windows environments, you can implement this policy setting to give users the right to perform chmod operations that change permissions, or the right to perform chown operations that take ownership, but do not give away ownership. Select one of the following options:

Allow only the file owner to change the mode or owner of the file (UNIX model)

Enables chmod and chown access checks to operate with UNIX-like behavior.

Allow the file owner and users with WRITE_DAC and WRITE_OWNER permissions to change the mode or owner of the file (Windows model)

Enables chmod and chown access checks to operate with Windows-like behavior.

Advanced ACL Settings

Treatment of 'rwx' permissions

In UNIX environments, rwx permissions indicate that a user or group has read, write, and execute permissions and that a user or group has the maximum level of permissions.

When you assign UNIX permissions to a file, no ACLs are stored for that file. Because a Windows system processes only ACLs, the PowerScale cluster must translate the UNIX permissions into an ACL when you view a file's permissions on a Windows system. This type of ACL is called a synthetic ACL. Synthetic ACLs are not stored anywhere; instead, they are dynamically generated and discarded as needed. If a file has UNIX permissions, you may notice synthetic ACLs when you run the ls file command to view a file’s ACLs.

When you generate a synthetic ACL, the PowerScale cluster maps UNIX permissions to Windows rights. Windows supports a more granular permissions model than UNIX does, and it specifies rights that cannot easily be mapped from UNIX permissions. If the PowerScale cluster maps rwx permissions to Windows rights, you must enable one of the following options:

Retain 'rwx' permissions

Generates an ACE that provides only read, write, and execute permissions.

Treat 'rwx' permissions as Full Control

Generates an ACE that provides the maximum Windows permissions for a user or a group by adding the change permissions right, the take ownership right, and the delete right.

Group Owner Inheritance

Operating systems tend to work with group ownership and permissions in two different PowerScale group owner from the file creator's primary group. If you enable a setting that causes the group owner to be inherited from the creator's primary group, you can override it on a per-folder basis by running the chmod command to set the set-gid bit. This inheritance applies only when the file is created. For more information, see the manual page for the chmod command.

Select one of the following options:

When an ACL exists, use Linux and Windows semantics, otherwise use BSD semantics

Specifies that if an ACL exists on a file, the group owner is inherited from the file creator's primary group. If there is no ACL, the group owner is inherited from the parent folder.

BSD semantics - Inherit group owner from the parent folder

Specifies that the group owner be inherited from the file's parent folder.

Linux and Windows semantics - Inherit group owner from the creator's primary group

Specifies that the group owner be inherited from the file creator's primary group.

chmod (007) On Files With Existing ACLs

Specifies whether to remove ACLs when running the chmod (007) command. Select one of the following options.

chmod(007) does not remove existing ACL

Sets 007 UNIX permissions without removing an existing ACL.

chmod(007) removes existing ACL and sets 007 UNIX permissions

Removes ACLs from files over UNIX file sharing (NFS) and locally on the cluster through the chmod (007) command. If you enable this setting, be sure to run the chmod command on the file immediately after using chmod (007) to clear an ACL. In most cases, you do not want to leave 007 permissions on the file.

Approximate Owner Mode Bits When ACL Exists

Windows ACLs are more complex than UNIX permissions. When a UNIX client requests UNIX permissions for a file with an ACL over NFS, the client receives an approximation of the file's actual permissions. Running the ls -l command from a UNIX client returns a more open set of permissions than the user expects. This permissiveness compensates for applications that incorrectly inspect the UNIX permissions themselves when determining whether to try a file-system operation. The purpose of this policy setting is to ensure that these applications go with the operation to allow the file system to correctly determine user access through the ACL. Select one of the following options:

Approximate owner mode bits using all possible group ACEs in ACL

Causes the owner permissions appear more permissive than the actual permissions on the file.

Approximate owner mode bits using only the ACE with the owner ID

Causes the owner permissions appear more accurate, in that you see only the permissions for a particular owner and not the more permissive set. This may cause access-denied problems for UNIX clients, however.

Approximate Group Mode Bits When ACL Exists

Select one of the following options for group permissions:

Approximate group mode bits using all possible group ACEs in ACL

Makes the group permissions appear more permissive than the actual permissions on the file.

Approximate group mode bits using only the ACE with the group ID

Makes the group permissions appear more accurate, in that you see only the permissions for a particular group and not the more permissive set. This may cause access-denied problems for UNIX clients, however.

Synthetic "deny" ACEs

The Windows ACL user interface cannot display an ACL if any deny ACEs are out of canonical ACL order. To correctly represent UNIX permissions, deny ACEs may be required to be out of canonical ACL order. Select one of the following options:

Do not modify synthetic ACLs and mode bit approximations

Prevents modifications to synthetic ACL generation and allows “deny” ACEs to be generated when necessary.

CAUTION:This option can lead to permissions being reordered, permanently denying access if a Windows user or an application performs an ACL get, an ACL modification, and an ACL set to and from Windows.

Remove “deny” ACEs from ACLs. This setting can cause ACLs to be more permissive than the equivalent mode bits

Does not include deny ACEs when generating synthetic ACLs.

Access check (utimes)

You can control who can change utimes, which are the access and modification times of a file. Select one of the following options:

Allow only owners to change utimes to client-specific times (POSIX compliant)

Allows only owners to change utimes, which complies with the POSIX standard.

Allow owners and users with ‘write’ access to change utimes to client-specific times

Allows owners as well as users with write access to modify utimes, which is less restrictive.

Read-only DOS attribute

Deny permission to modify files with DOS read-only attribute over Windows Files Sharing (SMB)

Duplicates DOS-attribute permissions behavior over only the SMB protocol, so that files use the read-only attribute over SMB.

Deny permission to modify files with DOS read-only attribute through NFS and SMB

Duplicates DOS-attribute permissions behavior over both NFS and SMB protocols. For example, if permissions are read-only on a file over SMB, permissions are read-only over NFS.

Displayed mode bits

Use ACL to approximate mode bits

Displays the approximation of the NFS mode bits that are based on ACL permissions.

Always display 777 if ACL exists

Displays 777 file permissions. If the approximated NFS permissions are less permissive than those in the ACL, you may want to use this setting so the NFS client does not stop at the access check before performing its operation. Use this setting when a third-party application may be blocked if the ACL does not provide the proper access.